Reland "Reduce locking in VideoReceiver and check the threading model."
This is a reland of c75f1e45093a8d5cc62937c7708b87aa5c5bf0b0.
Original change's description:
> Reduce locking in VideoReceiver and check the threading model.
>
> Note: This is a subset of code that was previously reviewed here:
> - https://codereview.webrtc.org/2764573002/
>
> * Added two notification methods, DecoderThreadStarting() and DecoderThreadStopped()
> * Allows us to establish a period when the decoder thread is not running and it is
> safe to modify variables such as callbacks, that are only read when the decoder
> thread is running.
> * Allows us to DCHECK thread guarantees/correctness.
> * Allows synchronizing callbacks from the module process thread and have them only
> active while the decoder thread is running.
> * The above, allows us to establish two modes for the thread,
> single-threaded-mutable and multi-threaded-const.
> * Using that knowledge, we can remove |receive_crit_| as well as locking for a
> number of member variables.
> * Removed |VCMFrameBuffer _frameFromFile| (unused).
> * Clean up several of my TODOs
>
> Bug: webrtc:7361, chromium:695438
> Change-Id: Id0048ee9624f76103c088d02825eb5c0d6c8913c
> Reviewed-on: https://webrtc-review.googlesource.com/55000
> Commit-Queue: Tommi <tommi@webrtc.org>
> Reviewed-by: Philip Eliasson <philipel@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22133}
Bug: webrtc:7361, chromium:695438
Change-Id: I32e1dc6c62cb30ad96e6366106f39fe415de49f1
Tbr: philipel@webrtc.org
Reviewed-on: https://webrtc-review.googlesource.com/56803
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22163}diff --git a/modules/video_coding/video_coding_impl.h b/modules/video_coding/video_coding_impl.h
index 8a442c8..3b692d1 100644
--- a/modules/video_coding/video_coding_impl.h
+++ b/modules/video_coding/video_coding_impl.h
@@ -143,7 +143,7 @@
VCMTiming* timing,
NackSender* nack_sender = nullptr,
KeyFrameRequestSender* keyframe_request_sender = nullptr);
- ~VideoReceiver();
+ ~VideoReceiver() override;
int32_t RegisterReceiveCodec(const VideoCodec* receiveCodec,
int32_t numberOfCores,
@@ -161,9 +161,6 @@
int32_t Decode(const webrtc::VCMEncodedFrame* frame);
- // Called on the decoder thread when thread is exiting.
- void DecodingStopped();
-
int32_t IncomingPacket(const uint8_t* incomingPayload,
size_t payloadLength,
const WebRtcRTPHeader& rtpInfo);
@@ -188,41 +185,72 @@
int64_t TimeUntilNextProcess() override;
void Process() override;
+ void ProcessThreadAttached(ProcessThread* process_thread) override;
void TriggerDecoderShutdown();
+ // Notification methods that are used to check our internal state and validate
+ // threading assumptions. These are called by VideoReceiveStream.
+ // See |IsDecoderThreadRunning()| for more details.
+ void DecoderThreadStarting();
+ void DecoderThreadStopped();
+
protected:
- int32_t Decode(const webrtc::VCMEncodedFrame& frame)
- RTC_EXCLUSIVE_LOCKS_REQUIRED(receive_crit_);
+ int32_t Decode(const webrtc::VCMEncodedFrame& frame);
int32_t RequestKeyFrame();
private:
- rtc::ThreadChecker construction_thread_;
+ // Used for DCHECKing thread correctness.
+ // In build where DCHECKs are enabled, will return false before
+ // DecoderThreadStarting is called, then true until DecoderThreadStopped
+ // is called.
+ // In builds where DCHECKs aren't enabled, it will return true.
+ bool IsDecoderThreadRunning();
+
+ rtc::ThreadChecker construction_thread_checker_;
+ rtc::ThreadChecker decoder_thread_checker_;
+ rtc::ThreadChecker module_thread_checker_;
Clock* const clock_;
rtc::CriticalSection process_crit_;
- rtc::CriticalSection receive_crit_;
VCMTiming* _timing;
VCMReceiver _receiver;
VCMDecodedFrameCallback _decodedFrameCallback;
- VCMFrameTypeCallback* _frameTypeCallback RTC_GUARDED_BY(process_crit_);
- VCMReceiveStatisticsCallback* _receiveStatsCallback
- RTC_GUARDED_BY(process_crit_);
- VCMPacketRequestCallback* _packetRequestCallback
- RTC_GUARDED_BY(process_crit_);
- VCMFrameBuffer _frameFromFile;
+ // These callbacks are set on the construction thread before being attached
+ // to the module thread or decoding started, so a lock is not required.
+ VCMFrameTypeCallback* _frameTypeCallback;
+ VCMReceiveStatisticsCallback* _receiveStatsCallback;
+ VCMPacketRequestCallback* _packetRequestCallback;
+
+ // Used on both the module and decoder thread.
bool _scheduleKeyRequest RTC_GUARDED_BY(process_crit_);
bool drop_frames_until_keyframe_ RTC_GUARDED_BY(process_crit_);
- size_t max_nack_list_size_ RTC_GUARDED_BY(process_crit_);
- VCMDecoderDataBase _codecDataBase RTC_GUARDED_BY(receive_crit_);
- EncodedImageCallback* pre_decode_image_callback_;
+ // Modified on the construction thread while not attached to the process
+ // thread. Once attached to the process thread, its value is only read
+ // so a lock is not required.
+ size_t max_nack_list_size_;
- VCMProcessTimer _receiveStatsTimer;
- VCMProcessTimer _retransmissionTimer;
- VCMProcessTimer _keyRequestTimer;
- QpParser qp_parser_;
- ThreadUnsafeOneTimeEvent first_frame_received_;
+ // Callbacks are set before the decoder thread starts.
+ // Once the decoder thread has been started, usage of |_codecDataBase| moves
+ // over to the decoder thread.
+ VCMDecoderDataBase _codecDataBase;
+ EncodedImageCallback* const pre_decode_image_callback_;
+
+ VCMProcessTimer _receiveStatsTimer RTC_GUARDED_BY(module_thread_checker_);
+ VCMProcessTimer _retransmissionTimer RTC_GUARDED_BY(module_thread_checker_);
+ VCMProcessTimer _keyRequestTimer RTC_GUARDED_BY(module_thread_checker_);
+ QpParser qp_parser_ RTC_GUARDED_BY(decoder_thread_checker_);
+ ThreadUnsafeOneTimeEvent first_frame_received_
+ RTC_GUARDED_BY(decoder_thread_checker_);
+ // Modified on the construction thread. Can be read without a lock and assumed
+ // to be non-null on the module and decoder threads.
+ ProcessThread* process_thread_ = nullptr;
+ bool is_attached_to_process_thread_
+ RTC_GUARDED_BY(construction_thread_checker_) = false;
+#if RTC_DCHECK_IS_ON
+ bool decoder_thread_is_running_ = false;
+#endif
};
} // namespace vcm